Yì 意 is the Chinese rendering for the Sanskrit term manas, which can be translated as “mind”, and comes from Buddhist psychology.
Manas or mānas-vijñāna 'मानस-विज्ञान (roughly "mind-knowledge" or “mind consciousness”, sometimes also rendered as “consciousness of self”) is one of the eight consciousnesses as outlined in the Yogacara and Consciousness-Only (Cittamatra) schools of Buddhist thought, which are no longer generally practiced as distinctive traditions but have heavily influenced many forms of Mahayana Buddhism, particularly in East Asia and Chan/Zen Buddhism.
Eight consciousnesses does not mean there are literally eight separate consciousnesses. Think of it more like a model that describes facets of consciousness. It’s a framework to help understand how the mind "works" in a way that can facilitate one’s practice.
Manas is sometimes equated to the concept of the ego in Western psychology, though it is not exactly the same. A simplified explanation is that manas is the aspect of consciousness that actively perceives and discriminates, taking input from other aspects of consciousness and creating distinctions and attachments to thoughts and ideas. My personal understanding at present is that manas is a filter of thoughts/experience that constructs the sense of self.
There is a rich tradition of comparing the mind to different animals, such as a monkey, an ox, or an elephant. I often think of my own mind as a hamster running furiously in a hamster wheel, expending a lot of energy going nowhere and doing nothing aside from exhausting myself. I’m trying to help that little hamster rest, wherever it may be.
Additional resources
- Understanding Our Mind - 50 Verses on Buddhist Psychology by Thich Nhat Hanh (Publisher link | WorldCat/public library | You can read an excerpt here: https://www.lionsroar.com/the-four-layers-of-consciousness/)
- Inside Vasubandhu’s Yogacara - A Practitioner’s Guide by Ben Connelly, with “Thirty Verses on Consciousness Only” translated from Sanskrit by Ben Connelly and Weijen Teng (Publisher link | WorldCat/public library)